Thomson thick X-ray absorption in a broad absorption line quasar, PG 0946+301

We present a deep ASCA observation of a broad absorption line quasar (BALQS Q) PG 0946+301. The source was clearly detected in one of the gas imaging s pectrometers, but not in any other detector. If BALQSOs have intrinsic X-ra y spectra similar to normal radio-quiet quasars, our observations imply tha t there is Thomson thick X-ray absorption (N-H greater than or similar to 1 0(24) cm(-2)) toward PG 0946+301. This is the largest column density estima ted so far toward a BALQSO. The absorber must be at least partially ionized and may be responsible for attenuation in the optical and UV. If the Thoms on optical depth toward BALQSOs is close to 1, as inferred here, then spect roscopy in hard X-rays with large telescopes like XMM would be feasible.